I need to set up
eth1 using these :
ip 10.5.15.200 netmast 255.255.255.128 mac address AA:6F:78:UI:34:34
and must be set up before
and default gateway must be the first usable address from network
Open the file
This sets the specific values. However at the moment it is unclear what you meant with your comment on the default gateway. Could you elaborate?
The gateway address can be any of the usable addresses within the 25 bit subnet here. It is usually the first, sometimes the last IPv4 address available.